Fan



Patented Aug. 25, 1931 UNITED STATES PATENT OFFICE EDWARDv R. HEWITT, OF MIDVALE, NEW JERSEY, ASSIGNOR TO INTERNTIONAL MOTOR COMPANY, 0F NEW YORK, N. Y., A CORPORATION OF DELAWARE FAN Application led May 4, 1929. Serial No. 360,338.

tation of the fan. Similarly, the power I 'e- :quired to drive such a fan varies with its speed. In some situations, as where a fan is associated with a radiator, it is advantageous to keep the air speed substantially constant regardless of the speed of the prime mover and it is also desirable to avoid an increase of power consumption when the fan is driven at higher speeds .by the prime mover. The principal object of the present invention is to provide a fan which shall satisfy the stated requirements and give substantially constant air speed for varying engine speeds and require substantially no greater power to drive 1t at higher engine speeds. A further object of the invention is to provide a multi-bladed fan in which the pitchA of all the blades shall change automatically and to the same extent under varying resistances, their positions being controlled by a yielding spring pressure which is applied uniformly vto each of the blades. Still another object of the invention is to transmit the force of the spring to the blades by means which reduce the power transmitted from the spring to the blades at higher engine speeds.

The inventionwill be described more parl ticularly in connection withthe embodiment illustrated in the accompanying drawings wherein:

- line 2-2 of Figure 1 and looking in the direction of the'arrows.

Figure 3 is a fragmentary view in vertical section through the improved fan taken on the plane indicated by the line 3 3 of Figure 2 and looking in the direction of the arrows. e

. Figure 4 is a view in plan of the fan shown in Figure l with the bladesin normal position.

Figure 5 is a View similar to Figure 4 but I showing the blades at a greater angle due to increased resistance.

While it `will be evident as this description proceeds that the principle of the invention may bek embodied in fans used for any purpose, for convenience it will be assumed that the embodiment illustrated in the drawings is that of a fan for use in association with a radiator of an internal combustion en e. Such a radiator is indicated conventiona y at a and the improved fan is shown as mounted adjacent to it and rotated from power applied to a pulley b, the speed of rotation being related to the speed o the prime mover. On the fan shaft c is secured two radially extendin arms c', o2, which in the case of a two-blad fan 'will `be diametrically opposed. On each of these arms is mounted pivotally'a blade d. Any number of arms and blades may be thus mounted. The invention is not concerned with the form or structure of the blade but in the interest of lightness and cheapness of manufacture, the blade may be formed hollow so that the arm c may extend through the end plates thereof and threaded into the circular flange c3 carried with the shaft. Each blade is so mounted on its supporting arm that it presents a larger superficial area to the air at one side of the axis than the other. This largersupericial area is found on the trailing portion of the blade having in mind the direction of rotation of the fan. The effect of such an unbalanced condition is that as the speed of rotation of the fan increases a greater air pressure will be built up on the trailing surface and tend to rotate the blade on its axis so as to more nearly bring the air surface in the plane of rotation. Such a movement-must,` of course, be resisted and yielding means are provided to resist with equal force rotation of all of the blades on their respective axes. Various forms of such yielding decertain advantages. The inner end plate e of each blade has secured thereto an arm f which carries a roller g. The rollers of each of the blades bear against afdisk which is 5 slidably mounted on the fan shaft c. On the end of the fan shaft is secured a nut lc and a spiral spring Z is interposed between the nut k and the disk z' so as to resist its sliding movement yieldin ly.

derstood that all of the blades .d are normally held at their minimum intended angle to the shaft by the pressure of the spring Z transmitted to all of the blades through the engagement of a disk i with the several rollers. This normal condition is illustrated in Figure 4. When the speed of rotation of the fan increases the increasing resistance on the trailing surface will cause the blades to rock simultaneously on their respective pivot arms but such angular movement is resisted yieldingly by the spring Z. A chan ed p angularity of the blades under this conditlon of higher speed is indicated in Figure 5. The resistance oiered to all of the blades is uniform because of the common connection to the single spring. Another feature of the invention resides in the disposition of the rollers g on their supports in such relation to the axes of the blades From the description given it will be unblades on their supports', and means operatively interposed between the blades and the spring whereby the force of the spring is applied to the blades with reduced everage upon increase of the angularity of the blades..

2. A fan comprising a rotating fan shaft, radially extending arms carried thereby, blades mounted pivotally on said arms, each blade having a greater air surface on its trailing face with respect to said support, an arm carried with each blade having a roller journaled therein, a disk mounted slidably 'on the fan shaft against which vsaid rollers bear and a spring operatively engaged with the disk to resist axial movement thereof, movement of the blades on the sup orts serving to move the rollers towards the an shaft thereby decreasing the edective leverage.

This speci cation signed this th day of April A. D. 1929.

' EDWARD' R. HEWITT.

' and the disk i that as the angularity of the Y blades increases the lever arms through which the force of the sprin Z is applied to the'blades decreases so t at at higher applied to the blades actually ecreases thereby making the adjustments at hi her speeds more sensitive. A's shown in igure 4 the axis of each roller g is disposed 0 nearly laterally with respect to the supporting arm c of each blade so that the force of the spring Z is transmitted to the blade with the maximum leverage. Asshown in Figure 5 after the blades have assumed a position of greater angularity each roller g moves inwardly with respect to the fan shaft c so that the pressure of the spring Z is transmitted to each blade through a smaller lever arm, thereby decreasing the power of application of the force.

Changes in details of construction may be made without varying the principle. The number ofblades and the supporting means therefor can be changed and the type of spring and its relation to the blades can also be altered by one skilled in the art without avoiding the invention as deiined in the accompanying claims.

What I claim is:

arms, blades mounted pivotally Von the respective arms, each of said blades presenting a greater air surface on the trailing side with res ct to its ivotal supports, a sprin to reslst yielding y angular movements o the speeds the eiective power of the s ring as 1. Afan shaft having a plurality of radial. 

